Door alarm



July 27, 1965 c. R. BALDWIN ETAL DOOR ALARM 2 Sheets-Sheet l Filed March6, 1961 JNVENTOM. ffhar/les R, Ba [div/n fifjys.

5? William Baldwin w 9 %%A United States Patent 3,197,588 DOGR ALARMCharles R. Baldwin, 1124 S. Adams, and William Baldwin, W. 4115 BroadSt, both of Spokane, Wash. Filed Mar. 6, 1961, Ser. No. 93,464 I Ciaim.(Ci. Nil-61.68)

The present invention relates to a door alarm adapted to set off analarm whenever an unauthorized attempt is made to open the door. It isthe principal purpose of our invention to provide an alarm device fordoors, the operation of which is controlled by the bolt or latch pinthat extends between the door and the adjacent Wall. Although notlimited thereto our invention is particularly adapted for use on thedoors of apartments and houses.

People frequently have the door latches so set that they can be openedfrom the inside but cannot be opened by turning the outside knob andfrequently the doors are not locked at all so that turning the outsideknob will move the bolt. This gives a prowler ready access without anywarning to those within the house. Even if the door lock is set so thatit can be opened by turning the inside knob but the outside knob is noteirective to withdraw the bolt, a prow-ler can, with very littledifliculty, force the bolt out of the socket and thus gain entrance. Ourinvention provides a simple effective means to give warning of suchunauthorized entry attempt in either case, before the door is opened.

It is also a purpose of our invention to provide an alarm operated bythe locking bolt of a door which is entirely free of any physicalconnection to the door itself apart from the bolt, and which is operatedby the bolt while the bolt is in position to hold the door closed.

Our invention embodies a simple complete unit that can be installed inthe wall adjacent to a door opening without defacing the door casing ortrim and requires no modification of the hardware commonly used in doorlocks now.

The nature and advantages of our invention will appear more fully fromthe following description and the accompanying drawings illustrating thepreferred form of the device. It should be understood, however, that thedrawings and description are illustrative only and that various minorchanges may be made within the scope of the claims :which define theinvention.

In the drawings:

FIGURE 1 is a fragmentary side view with parts broken away of a door andthe adjacent casing and wall showing our invention applied thereto;

FIGURE 2 is a front view of the alarm device when unmounted;

FIGURE 3 is a side view of the alarm control unit that is operated bythe locking bolt of the door;

FIGURE 4 is a face view of the alarm control unit as seen from the rightof FIGURE 3;

FIGURE 5 is a sectional view of the alarm device taken substantially onthe line 5-5 of FIGURE 2; and

FIGURE 6 is a wiring diagram showing the electrical connectionsnecessary for the door alarm.

Referring now to the drawings, our invention is shown as applied to adoor installation wherein the door casing is indicated at It) and theadjacent wall at 11, The door is indicated at 12 and the door knob at13. A typical door frame construction includes a main frame structuralmember 14, a casing member I5 and a door step 16. The door lockingmechanism includes a bolt or latch member 17 that is normally extended,as shown in FIG- URE l, and is spring pressed outward to this position.The door knob acts to retract the bolt into the door so that the doorcan be opened.

The door casing member is generally recessed to receive a striker plate18 that is conventional. Accord- 3,197,588 Patented July 27, 1965 ing toour invention this casing member 15 is further recessed to receive aswitch mounting member 19 which is a metal strip apertured to receivethe screws 20 (shown dotted in FIGURE 1) that secure the striker plate18. The striker plate 13 has an aperture 21 therein to receive the doorbolt 17. The member 19 has a U-shaped central portion 22 aligned withthe aperture 21. The casing member 15 and the frame member 14 areapertured to receive the portion 22 of the member 19.

A switch 23 is mounted on the member 19 in the center of the portion 22.The switch has a threaded sleeve 24 extending through the portion 22 andsecured therein by nuts 25 and 26. The nut 25 is preferably welded tothe portion 22. The switch has a stem 27 of insulating materialprojecting form the sleeve 24 toward the bolt 17 and adapted to engagethe bolt when the door is in closed position.

It will be noted that the switch 23 is a normally closed switch, asillustrated in FIGURES l and 6. There is a spring 28 which urges thestem 27 into position where a bridging member 29, carried by the stem27, engages two contacts 36 and 31 that are carried by two wiringterminals 32 and 33 of the switch 23. If the stem 27 is pushed againstthe spring 28 the bridging member 29 is moved away from the contacts 3%and 31 to break the circuit between the terminals 32 and 33.

As illustrated diagrammatically in FIGURE 6 of the drawing, the switch23 is connected in series with an alarm device, such as a bell 34 and amanual shut off switch 35, across a source of electric current 36 suchas a dry cell battery. When both switches 23 and 35 are closed, currentis supplied from the source 36 to the alarm device to actuate the alarm.The form of alarm 34 and the connections thereto are quite simple andmay, of course, be varied by one skilled in the art to suit theparticular need as to type of alarm. 'We have found, however, that alarmbells of simple construction are readily available. Such an alarm bell34 is shown in FIGURE 5 of the drawings, as mounted upon a face plate 37by a bracket 38. The face plate 37 is in turn mounted upon the mountingbars 39 and 49 of the switch 35 which is a conventional householdswitch, such as is commonly used to control the lighting circuits in ahome.

The switch 35 is mounted through the wall to an open sided box 4 byscrew bolts 42. which are covered by the face plate 37. Other screwbolts 43 secure the mounting bars 39 and 46) to the face plate. A pairof screw bolts 44 secure the ends of the bracket 38 to the face plate37.

The face plate 37 has a large aperture 45 therein between the screwbolts 44, and this aperture 45 is directly in front of the alarm 34. Ascreen 46 is laid between the face plate 37 and the alarm 34 and issecured in place against the face plate by the screw bolts 44 and theends of the bracket 38. The screw bolts 44 pass through the screen 46and the bracket 38 and are provided with nuts 47. The box 41 is threadedto receive the screw bolts 42 and the mounting bars 39 and 40 areapertured for these screw bolts. The mounting bars 39 and 40 arethreaded to receive the screw bolts 43.

A dry cell battery mounting unit 48 is mounted on the box 41. This unit48 has spring clips 49 between which a battery 5%) is held, The unit 48includes a bracket 51 resting on a pad 52 of yielding material. One end52 of the bracket 51 is provided with a seat 53 for one battery contactand the other end 54 of the bracket 51 has an insulated contact 55 inthe form or a coiled spring to engage the contact surface at the otherend of the battery. The contact 55 is mounted on the end 54 by a plug 56of insulating material to which a wiring terminal 57 is also mounted.The contact 55 and the terminal 57 are electrically connected throughthe plug to each other.

The current path is essentiallly as shown in FIGURE 6 of the drawings.One terminal of the alarm 34 and the seat 53 for the one contact of thebattery 50 are grounded to the box 41. The other terminal of the alarm34 is.

connected through the switch 35 to one terminal of the switch 23. Theother terminal of the switch 23 is connected to the wiring terminal 57and through this terminal and the contact 55 to the ungrounded end ofthe battery 50.

Thus it is evident that when the switch 35 is closed, any closure of theswitch 23 will energize the alarm 34. When the door bolt 17 is in thelocking position shown in FIGURE 1, it holds the switch bridging member29 away from the contacts 30 and 31 and the alarm 34 cannot beenergized. However, any slight movement of the bolt 17, sufiieient topermit the member 29 to engage the contacts 30 and 31, will energize thealarm 34 by closing the only open point in the electrical circuitbetween the battery 50 and the alarm 34. The switch 23 can be adjustedby loosening the nut 26 and then turning the entire switch 23 to move itendwise with respect to the door bolt 17.

Note that the stem 27, which is of a tough hard insulating material, hasa slot 27a across its end so a screw driver may be used to turn theswitch sleeve 24 in the nut 25. When the alarm system is installed at adoor the original setting of the sleeve 24 in the nut 25 is made so thatthe door bolt 17, fully extended, will be sure to hold the member 29 inthe stem 27 out of contact with the contacts 30 and 31. Now to make thealarm system most sensitive, a screw driver can be used to move the stem27 away from the door knob 17 until the slightest movement of the doorknob 17 will result in the member 29 bridging the contacts 30 and 31 toenergize the alarm 34. It is easy to adjust the stem 27 until thedesired sensitivity is obtained, The alarm should always be energizedbefore the bolt 17 is retracted far enough to clear the striker plateand permit opening of the door. If the alarm is to be made inoperative,it is only necessary to open the switch 35.

It is believed to be evident from the foregoing description that oursafety alarm device for doors provides a simple device operatingdirectly from the door bolt that keeps the door from opening, in such away as to energize and sound the alarm while the door is held againstclosing by the bolt. The novel construction employed makes the deviceeasy to install, adjust and mainoneness tain. The screened opening inthe switch face plate prevents muffling of the sound from the alarm andpermits the use of a small compact a'la-rm bell.

Having described our invention, we claim:

A door bolt controlled device comprising:

a switch mounted in an aperture recessed behind a door striker plate ina fixed position, said switch having a projec stem extending from saidaperture into the recess which receives the door bolt, said stem beingmovable toward or away from said aperture;

a mounting bracket secured to said switch and locked in place by saidstriker plate;

said switch having a pair of contacts closed when said stem ispositioned outwardly away from said aperture;

a spring in said switch operatively connected to said contacts tonormally bias said contacts to a closed position;

said bracket and said switch being connected by a threaded sleeve on theswitch and a matching threaded nut fixed on the bracket; and

wherein said switch includes mechanical means for linking any rotationalmovement of said stem with said sleeve so that the switch and its stemcan be adjusted endwise on the bracket by rotation of said stem.

References Cited by the Examiner UNITED STATES PATENTS 463,793 11/91Hodgson et al. 20061.68

759,814 5/04 Knapp 20061.68 1,399,170 12/21 Vandevelde. 1,608,201 11/26Coburn et al. 1,627,357 5/27 Townley 20061.68 1,923,450 8/33 Miller200-159 2,523,125 9/50 Ley 200169 2,615,083 10/52 Krueger. 2,824,3002/58 Rand 340-274 2,835,760 5/58 Ringwald 20061.82 3,011,163 11/61 Britt340-274 FOREIGN PATENTS 378,980 8/23 Germany. 416,658 7/25 Germany.

NETL C. READ, Primary Examiner.

E. JAMES SAX, Examiner.

